Camshaft with phasing device for multi-cylinder internal combustion engine with poppet valves

Abstract

A camshaft for a multi-cylinder internal combustion engine with poppet valves, comprising a main body, which is rotatable with respect to a first rotation axis, a first disk and means of the hydraulic type for varying the timing of said first disk with respect to said main body.

The invention claimed is: 
     
       1. A camshaft for a multi-cylinder internal combustion engine with poppet valves, comprising a main body, which is rotatable with respect to a first rotation axis, a first disk and means for varying the timing of said first disk with respect to said main body;
 wherein said main body is shaped so as to define a circuit for a pressurized fluid; 
 wherein said camshaft comprises first thrust means and second thrust means, which are adapted to be operated by said pressurized fluid and translated along respective translation directions, said first and said second thrust means being adapted to engage, on thrust, a first counterpart and a second counterpart, respectively, of said first disk; 
 wherein the engagement on thrust of said first counterpart by said first thrust means and of said second counterpart by said second thrust means, respectively, results in said first disk being rotated with respect to a first rotation axis in a first rotation direction and in a second rotation direction, respectively, opposed to said first rotation direction, and therefore, in the relative angle between said first disk and said main body being varied; 
 wherein said main body comprises an internal cavity for collecting the pressurized fluid and a first pipe for conveying the pressurized fluid exiting said internal cavity towards said first thrust means and second thrust means, wherein a switch is housed in said first pipe, which is movable between a first position and a second position, and wherein, when said switch is in said first position, said second thrust means are operated by the pressurized fluid and engage, on thrust, said second counterpart, while when said switch is in said second position, said first thrust means are operated by the pressurized fluid and engage, on thrust, said first counterpart; 
 and wherein said switch is translatable by centrifugal force along a radial direction to said first rotation axis depending on the angular speed of said main body. 
 
     
     
       2. The camshaft according to  claim 1 , wherein said main body comprises a second pipe, which puts said internal cavity into communication with the outside. 
     
     
       3. The camshaft according to  claim 1 , wherein first elastic contrast means are housed in said first pipe and arranged so that the translational switching of said switch from said first position to said second position, is carried out against the elastic resistance exerted by said first elastic contrast means and in that the translational switching of said switch from said second position to said first position, is promoted by the elastic thrust exerted by said first elastic contrast means. 
     
     
       4. The camshaft according to  claim 1 , wherein said switch comprises a slide valve, wherein said first thrust means and second thrust means are housed in a third pipe and a fourth pipe, respectively, each in fluid communication with said first pipe, wherein said slide valve is shaped so that, when positioned in said first position, said first pipe and said third pipe are put into communication so as to define a closed circuit, which allows the flow of said hydraulic fluid from said first pipe to said third pipe and from said third pipe to said first pipe while said first pipe and said fourth pipe are put into communication so as to define a blind circuit, which allows the flow of said hydraulic fluid only from said first pipe to said fourth pipe, and wherein said slide valve is shaped so that, when positioned in said second position, said first pipe and said third pipe are put into communication so as to define a blind circuit, which allows the flow of said hydraulic fluid only from said first pipe to said third pipe while said first pipe and said fourth pipe are put into communication so as to define a closed circuit, which allows the flow of said hydraulic fluid from said first pipe to said fourth pipe and from said fourth pipe to said first pipe. 
     
     
       5. The camshaft according to  claim 4 , wherein said slide valve comprises a substantially cylindrical hollow body with a first through hole and a second through hole obtained in the outer wall of said hollow body for connecting the inside of said hollow body to the outside of said hollow body. 
     
     
       6. The camshaft according to  claim 5 , wherein said third pipe and said fourth pipe comprise a first secondary pipe and a second secondary pipe and a third secondary pipe and a fourth secondary pipe, respectively, wherein with said slide valve in said first position, said first secondary pipe and said second secondary pipe are put into communication with said first through hole and said first pipe, respectively, said second through hole is put into communication with said third secondary pipe, while the communication between said fourth secondary pipe and said first pipe is obstructed by the side wall of said hollow body, and wherein, with said slide valve in said second position, said third secondary pipe and said fourth secondary pipe are put into communication with said second through hole and said first pipe, respectively, said first through hole is put into communication with said first secondary pipe, while the communication between said second secondary pipe and said first pipe is obstructed by the side wall of said hollow body. 
     
     
       7. The camshaft according to  claim 4 , wherein said first and second thrust means comprise a first piston and a second piston housed in said third pipe and in said fourth pipe, respectively. 
     
     
       8. The camshaft according to  claim 7 , wherein second elastic contrast means and third elastic contrast means are housed in said third pipe and in said fourth pipe, respectively, and in that the thrust engagement of said first counterpart and said second counterpart by said first piston and said second piston, respectively, is contrasted by the elastic resistance exerted by said second elastic contrast means and said third elastic contrast means, respectively. 
     
     
       9. The camshaft according to  claim 1 , wherein a substantially cylindrical hollow insert is housed inside said main cam body, wherein the internal cavity of said hollow insert is in communication with the internal cavity of said main body, and wherein said hollow insert comprises a through hole obtained in the outer wall thereof and positioned so as to put into communication said second pipe with the internal cavity of said hollow insert. 
     
     
       10. The camshaft according to  claim 1 , wherein a first non-return valve is housed in said second pipe. 
     
     
       11. The camshaft according to  claim 6 , wherein a second non-return valve and a third non-return valve are housed inside said first secondary pipe and said third secondary pipe, respectively. 
     
     
       12. An internal combustion engine for a motor vehicle with a rideable saddle, comprising a drive shaft, at least one camshaft according to  claim 1 , wherein the rotation of said main body with respect to said first rotation axis results in the actuation of one or more suction or discharge valves, wherein said engine comprises drive means interposed between said drive shaft and said first disk of said camshaft so that the rotation of the drive shaft generates a rotation of said main body of said at least one first camshaft. 
     
     
       13. The internal combustion engine according to  claim 12 , wherein said first disk of said at least one camshaft is kinematically connected to said drive shaft by means of a drive chain or belt.